Laravel/Eloquent Collection method to sort by a comma-separated string of IDs. Any models which do not appear in the given order are added to the end in ID order.

BaseCollection.php

<?php

use Illuminate\Database\Eloquent\Collection;

class BaseCollection extends Collection {

  public function sortByOrder($order, $delimeter = ',')
  {
    $order = is_array($order) ? $order : explode($delimeter, $order);
		
    return $this->sortBy(function($item) use ($order) {
      $found = array_search($item->id, $order);
      return $found === false ? 99999 + $item->id : $found;
    });
  }

}

usage.php

<?php

// I recommend you set the usage on a base model, and extend the base model,
// that way all your models benefit
class BaseEloquent extends Eloquent {
  public function newCollection(array $models = array())
  {
    return new BaseCollection($models);
  }
}

$property = Property::with('rooms')->get();

$property->roomOrder;
// "9,7,4,5,6,8,2"

$property->rooms->sortByOrder($property->roomOrder);